// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// AlignedMemory is a POD type that gives you a portable way to specify static
// or local stack data of a given alignment and size. For example, if you need
// static storage for a class, but you want manual control over when the object
// is constructed and destructed (you don't want static initialization and
// destruction), use AlignedMemory:
//
//   static AlignedMemory<sizeof(MyClass), ALIGNOF(MyClass)> my_class;
//
//   // ... at runtime:
//   new(my_class.void_data()) MyClass();
//
//   // ... use it:
//   MyClass* mc = my_class.data_as<MyClass>();
//
//   // ... later, to destruct my_class:
//   my_class.data_as<MyClass>()->MyClass::~MyClass();
//
// Alternatively, a runtime sized aligned allocation can be created:
//
//   float* my_array = static_cast<float*>(AlignedAlloc(size, alignment));
//
//   // ... later, to release the memory:
//   AlignedFree(my_array);
//
// Or using unique_ptr:
//
//   std::unique_ptr<float, AlignedFreeDeleter> my_array(
//       static_cast<float*>(AlignedAlloc(size, alignment)));

#ifndef BASE_MEMORY_ALIGNED_MEMORY_H_
#define BASE_MEMORY_ALIGNED_MEMORY_H_

#include <stddef.h>
#include <stdint.h>

#include "base/base_export.h"
#include "base/compiler_specific.h"

#if defined(COMPILER_MSVC)
#include <malloc.h>
#else
#include <stdlib.h>
#endif

namespace base {

// AlignedMemory is specialized for all supported alignments.
// Make sure we get a compiler error if someone uses an unsupported alignment.
template <size_t Size, size_t ByteAlignment>
struct AlignedMemory {
};

#define BASE_DECL_ALIGNED_MEMORY(byte_alignment)                                  \
    template <size_t Size>                                                        \
    class AlignedMemory<Size, byte_alignment> {                                   \
    public:                                                                       \
        ALIGNAS(byte_alignment)                                                   \
        uint8_t data_[Size];                                                      \
        void* void_data() { return static_cast<void*>(data_); }                   \
        const void* void_data() const { return static_cast<const void*>(data_); } \
        template <typename Type>                                                  \
        Type* data_as()                                                           \
        {                                                                         \
            return static_cast<Type*>(void_data());                               \
        }                                                                         \
        template <typename Type>                                                  \
        const Type* data_as() const                                               \
        {                                                                         \
            return static_cast<const Type*>(void_data());                         \
        }                                                                         \
                                                                                  \
    private:                                                                      \
        void* operator new(size_t);                                               \
        void operator delete(void*);                                              \
    }

// Specialization for all alignments is required because MSVC (as of VS 2008)
// does not understand ALIGNAS(ALIGNOF(Type)) or ALIGNAS(template_param).
// Greater than 4096 alignment is not supported by some compilers, so 4096 is
// the maximum specified here.
BASE_DECL_ALIGNED_MEMORY(1);
BASE_DECL_ALIGNED_MEMORY(2);
BASE_DECL_ALIGNED_MEMORY(4);
BASE_DECL_ALIGNED_MEMORY(8);
BASE_DECL_ALIGNED_MEMORY(16);
BASE_DECL_ALIGNED_MEMORY(32);
BASE_DECL_ALIGNED_MEMORY(64);
BASE_DECL_ALIGNED_MEMORY(128);
BASE_DECL_ALIGNED_MEMORY(256);
BASE_DECL_ALIGNED_MEMORY(512);
BASE_DECL_ALIGNED_MEMORY(1024);
BASE_DECL_ALIGNED_MEMORY(2048);
BASE_DECL_ALIGNED_MEMORY(4096);

#undef BASE_DECL_ALIGNED_MEMORY

BASE_EXPORT void* AlignedAlloc(size_t size, size_t alignment);

inline void AlignedFree(void* ptr)
{
#if defined(COMPILER_MSVC)
    _aligned_free(ptr);
#else
    free(ptr);
#endif
}

// Deleter for use with unique_ptr. E.g., use as
//   std::unique_ptr<Foo, base::AlignedFreeDeleter> foo;
struct AlignedFreeDeleter {
    inline void operator()(void* ptr) const
    {
        AlignedFree(ptr);
    }
};

} // namespace base

#endif // BASE_MEMORY_ALIGNED_MEMORY_H_
